Method for manufacturing a narrow magnetic read width current perpendicular to plane magnetoresistive sensor

ABSTRACT

A method for manufacturing a magnetic read head having a very narrow track width. The method includes the use of a non-Si containing photoresist to form a mask prior to ion milling to define the track-width of the sensor. Previously only Si-containing resists were used. The Si in the resist turned to an oxide, which allowed the photoresist to withstand the reactive ion etching used for image transfer to an underlying hard mask. The Si-containing resist, however, has limitations as to how small the mask can be made. It has been found that a non-Si-containing resist provides better resolution at very narrow track-width definition, and also provides good temperature resistance. Some modifications to the process allow the non-Si-containing resist to be used in the construction of the magnetic read sensor.

FIELD OF THE INVENTION

The present invention relates to magnetoresistive sensors and more particularly to a sensor manufactured by a process that allows the sensor to be formed with a very small magnetic read width.

BACKGROUND OF THE INVENTION

The heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.

The write head includes at least a coil, a write pole and one or more return poles. When a current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the write pole, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic disk, thereby recording a bit of data. The write field, then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head.

A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor, or a Tunnel Junction Magnetoresisive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The sensor includes a nonmagnetic conductive layer (if the sensor is a GMR sensor) or a thin nonmagnetic, electrically insulating barrier layer (if the sensor is a TMR sensor) sandwiched between first and second ferromagnetic layers, hereinafter referred to as a pinned layer and a free layer. Magnetic shields are positioned above and below the sensor stack and can also serve as first and second electrical leads so that the electrical current travels perpendicularly to the plane of the free layer, spacer layer and pinned layer (current perpendicular to the plane (CPP) mode of operation). The magnetization direction of the pinned layer is pinned perpendicular to the air bearing surface (ABS) and the magnetization direction of the free layer is located parallel to the ABS, but free to rotate in response to external magnetic fields. The magnetization of the pinned layer is typically pinned by exchange coupling with an antiferromagnetic layer.

When the magnetizations of the pinned and free layers are parallel with respect to one another, scattering of the conduction electrons is minimized and when the magnetizations of the pinned and free layer are antiparallel, scattering is maximized. In a read mode the resistance of the spin valve sensor changes about linearly with the magnitudes of the magnetic fields from the rotating disk. When a sense current is conducted through the spin valve sensor, resistance changes cause potential changes that are detected and processed as playback signals.

In the push to increase data density sensors have been required to be formed with ever narrower read widths. The read width can be determined by the width of the layers such as the electrically conductive spacer or barrier layer sandwiched between the pinned and free layers. However, certain manufacturing limitations have prevented further narrowing of the read width. Therefore, there remains a need for a method for reducing the read width of a magnetoresistive sensor in order to further increase track density and data density.

SUMMARY OF THE INVENTION

The present invention provides a method for manufacturing a magnetic read head having a very narrow track width. The method includes depositing a plurality of sensor layers, depositing a non-Si-containing photoresist, patterning the photoresist and performing an ion milling to define a magnetic read head.

The use of the non-Si-containing photoresist advantageously allows the sensor to be formed with a narrow track width than would be possible with a Si-containing photoresist as was previously used in the construction of magnetic read heads. This is because the non-Si-containing photoresit has better resolution and improved depth of focus as compared with the previously used Si-containing photoresist. The non-Si containing photoresist also provides tolerance of high temperatures such as those needed for atomic layer deposition and chemical vapor deposition.

Certain manufacturing process changes that make possible the use of a non-Si-containing resist include the use of a Si containing Bottom Anti-Reflective Coating beneath the non-Si-containing photoresist to improve RIE selectivity during the image transfer process. In addition, adding a noble gas to the CO, chemistry of the reactive ion etching (during image transfer) helps to avoid early consumption of the non-Si-containing photoresist. A glancing ion milling assisted CMP liftoff process can also be useful in removing the remaining mask layers at very small sensor widths, which may not be possible using CMP alone.

These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the Figures in which like reference numerals indicate like elements throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings which are not to scale.

FIG. 1 is a schematic illustration of a disk drive system in which the invention might be embodied;

FIG. 2 is an ABS view of a slider illustrating the location of a magnetic head thereon;

FIGS. 3 is an ABS view of an example of a magnetoresistive sensor that might be constructed by a method of the present invention;

FIGS. 4-12 are ABS views of a magnetoresistive sensor in various intermediate stages of manufacture illustrating a method of manufacturing a magnetoresistive sensor using a single layer mask;

FIGS. 13-20 are ABS views of a magnetoresistive sensor in various intermediate stages of manufacture illustrating a method of manufacturing a magnetoresistive sensor using a double layer mask; and

FIGS. 21-28 are ABS views of a magnetoresistive sensor in various intermediate stages of manufacture illustrating a method of manufacturing a magnetoresistive sensor using a tri-layer mask.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein.

Referring now to FIG. 1, there is shown a disk drive 100 embodying this invention. As shown in FIG. 1, at least one rotatable magnetic disk 112 is supported on a spindle 114 and rotated by a disk drive motor 118. The magnetic recording on each disk is in the form of annular patterns of concentric data tracks (not shown) on the magnetic disk 112.

At least one slider 113 is positioned near the magnetic disk 112, each slider 113 supporting one or more magnetic head assemblies 121. As the magnetic disk rotates, slider 113 moves radially in and out over the disk surface 122 so that the magnetic head assembly 121 may access different tracks of the magnetic disk where desired data are written. Each slider 113 is attached to an actuator arm 119 by way of a suspension 115. The suspension 115 provides a slight spring force which biases slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator means 127. The actuator means 127 as shown in FIG. 1 may be a voice coil motor (VCM). The VCM comprises a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by controller 129.

During operation of the disk storage system, the rotation of the magnetic disk 112 generates an air bearing between the slider 113 and the disk surface 122 which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension 115 and supports slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation.

The various components of the disk storage system are controlled in operation by control signals generated by control unit 129, such as access control signals and internal clock signals. Typically, the control unit 129 comprises logic control circuits, storage means and a microprocessor. The control unit 129 generates control signals to control various system operations such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide the desired current profiles to optimally move and position slider 113 to the desired data track on disk 112. Write and read signals are communicated to and from write and read heads 121 by way of recording channel 125.

With reference to FIG. 2, the orientation of the magnetic head 121 in a slider 113 can be seen in more detail. FIG. 2 is an ABS view of the slider 113, and as can be seen the magnetic head including an inductive write head and a read sensor, is located at a trailing edge of the slider. The above description of a typical magnetic disk storage system and the accompanying illustration of FIG. 1 are for representation purposes only. It should be apparent that disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders.

FIG. 3 shows an example of a magnetoresistive sensor structure 300 that could be constructed according to a method of the present invention. The sensor structure 300 is seen as viewed from the air bearing surface (ABS). The sensor 300 includes a sensor stack 302 that is sandwiched between first and second, electrically conductive, magnetic shields 304, 306 that also function as electrically conductive leads.

The sensor stack 302 can include a non-magnetic layer 308 that is sandwiched between a magnetic pinned layer structure 310 and a magnetic free layer structure 312. The non-magnetic layer 308 can be an electrically conductive material, if the sensor 300 is a Giant Magnetoresistive (GM R) sensor, and can be a thin electrically insulating material layer if the sensor structure 300 is a Tunnel Junction Sensor (TMR).

The pinned layer structure 310 can include first and second magnetic layers 314, 316 with a non-magnetic, antiparallel coupling layer such as Ru 318 sandwiched between the first and second magnetic layer 314, 318. The first magnetic layer 314 has its magnetization pinned in a first direction perpendicular to the ABS. This pinning is a result of exchange coupling with a layer of antiferromagnetic material 320 such as IrMn. The second magnetic layer 316 has its magnetization pinned in a second direction that is antiparallel with the first direction as a result of antiparallel coupling between the first and second magnetic layers 314, 316 across the antiparallel coupling layer 318.

The magnetic free layer 312 has a magnetization that is biased in a direction that is generally parallel with the ABS, but that is free to move in response to a magnetic field. The biasing of the free layer is provided by a magnetostatic coupling with first and second hard magnetic bias layers 322, 324. One or more seed layers 326 may be provided at the bottom of the sensor stack 302 in order to ensure a desired grain growth of the other layers of the sensor stack 302 deposited thereon. In addition a capping layer such as Ta 328 may be provided at the top of the sensor stack to protect the underlying layers during manufacture. In addition, thin insulation layers 330 is provided at either side of the sensor stack 302 and across at least the bottom lead/shield 304 in order to prevent sense current from being shunted through the magnetic bias layers 322, 324. The sensor structure 300 has a read width 322 that is determined by the width of the layers of the sensor stack 302, and especially by the width of the layers at the location of the spacer layer 308. This read width 332 can be advantageously made very small by a novel manufacturing process that will be described herein below. It should be pointed out that the sensor structure 300 is by way of example as various other forms of sensor structure could also be manufactured by the method of the present invention and would fall within the scope of the invention as well.

A basic requirement to achieve higher areal density is to reduce the physical magnetic read width 332 of the sensor 300. One method that has been used to define the read width of sensors is to use reactive ion etching (RIE) to image transfer a photo resist mask into an ion mill hard mask and then use the ion mill to pattern the hard mask image into the sensor. The success of this method requires that the photoresist mask height is sufficient to be image transferred into the ion mill hardmask. At widths of 40 nm or greater, the current lithographic approach is to use a silicon-containing photoresist to serve as an effective imaging layer to pattern a hardmask that consists of a material such as DURIMIDE® and carbon. A major advantage of silicon containing imaging resists is RIE selectivity. In the presence of O₂ or CO₂ RIE chemistries, the Si component of the imaging photoresist will oxidize to form SiO₂. In this form, the imaging photoresist will be resistant to further etching and, therefore, will effectively allow the patterning of the hard mask and subsequently the patterning of the sensor. After patterning of the sensor, ALD alumina deposition is done followed by hard bias.

There is, however, a drawback to the above process for use in defining sensors having very small read widths. At magnetic read widths smaller than 40 nm, major challenges with the silicon-containing resist result in an inability to further reduce the read width. This is mostly due to the photoresist reaching its resolution limit and to poor depth of focus properties of the Si-containing photoresist, which results in more line-edge roughness and not enough imaging photoresist to successfully image transfer the photoresist pattern into the hard mask.

FIGS. 4-12, illustrate a method for manufacturing a magnetoresistive sensor, according to a first embodiment of the invention which overcomes the limitations of the above described process. With reference to FIG. 4, a first magnetic shield/lead 402 is formed of an electrically conductive, magnetic material such as NiFe. A series of sensor layers 404 is deposited over the first shield/lead 402. These sensor layers 404 can correspond with the layers of the sensor stack 302 described above, but could include additional or other layers as well. A layer of material that is resistant to chemical mechanical polishing (CMP stop layer) 406 is deposited over the sensor layers 404. This layer 406 is, however, optional. The CMP stop layer 406 can be an electrically conductive material such as Ru, Rh, Ir or diamond like carbon (DLC).

A layer of photoresist 408 is then deposited over the mask 406. This photoresist layer 408 is a non-Si containing photoresist, such as JSR 1891 which is available from JSR MICRO, INC®. Such a non-Si containing photoresists achieves higher resolution than previously used Si containing resists. In addition, such non-Si containing photoresists have a higher heat resistance, which is necessary to withstand chemical vapor deposition (CVD) and/or atomic layer deposition (ALD) processes such as will be used in the construction of the read sensor structure as will be described herein below. Such non-Si containing photoresists also achieve better depth of focus than Si-containing photoresists. Such a non-Si-containing photoresist also has a better dissolution rate than previously used photoresist, has similar reactive ion etching selectivity to optional DLC and BARC materials (described below) and, perhaps most importantly, is soluble in NMP solution, which will further assist in liftoff at smaller read widths.

With reference now to FIG. 5, the photoresist layer 408 is photolithographically patterned and developed to form a photoresist mask having a width that defines a read width of a yet to be formed sensor. The photoresist layer 408 is made as thin as possible to maximize photolithographic resolution, while still being sufficiently thick to withstand an ion milling process (described below) for forming the sensor width. After the photoresist 408 has been patterned as shown, a quick reactive ion etching can be performed to transfer the image of the photoresist mask onto the underlying CMP stop layer 406, if DLC material is used for the CMP stop layer 406. Moreover, with or without DLC, a reactive ion etching (RIE) using O₂ or CO₂ with noble gaseous such as N₂, He, Ar, Xe, etc., for example, can be used to further reduce the photoresist mask's trackwidth (RIE slimming). A CO₂ or CO₂ with the noble gas is most preferred for RIE slimming.

With reference now to FIG. 6, an ion milling is performed to remove portions of the sensor material 404 that are not protected by the photoresist mask layer 408 and the optional CMP stop layer 406 to form a sensor 404 with a desired read width. Then, with reference to FIG. 7, a thin layer of non-magnetic, electrically insulating material such as alumina 702 is deposited. This insulation layer 702 is preferably deposited by a conformal deposition process such as chemical vapor deposition (CVD) or atomic layer deposition (ALD). A hard magnetic material 704 is then deposited over the insulation layer 702. The hard magnetic material 704 provides the hard bias layers 322, 324 described above with reference to FIG. 3, and the insulation layer 702 corresponds with the insulation layers 330 of FIG. 3. Therefore, the insulation layer 702 is preferably deposited thick enough to provide robust, reliable electrical insulation between the hard magnetic material 704 and the bottom shield 402 and sensor layers 404, while also being sufficiently thin to maximize magnetostatic coupling between the hard magnetic material 704 and the sensor layers 404 for improved free layer biasing.

It can be seen in FIG. 7, that after ion milling to form the sensor 404 and after depositing the layers 702, 704, a certain amount of the mask material 408 remains. In order to complete the formation of the sensor, the remaining mask layer 408 must be removed. It can also be seen the layers 702, 704 extend over the sensor 404, CMP stop layer 406 and remaining mask layer 408.

The mask layers 408 can be removed by a chemical liftoff process such as by coating with a hot NMP solution (N-Methyl Pyrrolidone) followed by snow cleaning (high pressure CO, spray) to remove resist and fences. However, in order for such a liftoff process to work, the NMP solution must be able to reach the mask 408. This means that a certain amount of the layers 702, 704 must be removed or exposed to allow the NMP solution to access the mask 408.

A wrinkle bake step can be used to form cracks where NMP can reach the mask to remove a greater portion of materials of the mask layers 408 in the field and grid areas. Liftoff is further enhanced by the use of the non-Si-containing resist, which is soluble in NMP. Due to re-deposition that formed during ion milling, in the track area it can be difficult to remove the mask layers at small dimensions. A chemical mechanical polishing process can be used to remove the portion of the layers 704, 702 that extend over the mask 408. This would require either inserting a CMP stop layer such as Ta with Rh, Ru or Ir during the hard magnetic material deposition or separately such as DLC. While CMP assisted lift-off is a preferred method at wider read width dimensions, at very narrow dimensions an ion milling assisted lift-off (UM) can also be used in conjunction with CMP to remove the layers 704, 702 that extend over the mask 408.

In this case an ion milling process in conjunction with CMP can be used to provide access to the mask 408 for the chemical liftoff. If ion milling is used, a bi-layer consisting of a CMP stop layer 706 and an ion milling resistant layer 708 is deposited on the top layer of the hard magnetic material 704. The ion milling resistant layer 708 protects the CMP stop layer 706 on the flat portion of the hard bias layer 704 during ion milling assisted lift-off. The ion milling resistant layer 708 is later removed during CMP. The CMP's slurry will remove the ion milling resistant layer. Materials suitable for use as a CMP stop layer 406 are Rh, Ir, and Ru. Examples of suitable materials for an ion milling resistant layer 708 include Ta, Al₂O₃, Si₃N₄, SiO₂, Ta₂O₅ or DLC.

With reference to FIG. 8, an ion milling is performed at a glazing angle as indicated by arrows 802. The glazing angle ion milling is an ion milling that is performed at an angle that is perpendicular with or nearly perpendicular with normal, or in other words is parallel or nearly parallel with the plane of the as deposited layers such as layers 402, 404, 406, 408, 702 and 704. To this end, the ion milling can be performed at an angle of 0 to 30 degrees relative to horizontal (i.e. relative to the planes of the as deposited layers as much as possible without damage to the substrate fixture). This glazing angle ion milling preferentially removes vertically aligned portions of the layer 704, thereby removing the material 704 from the sides of the mask 408 while leaving the desired hard bias layers 704 at the sides of the sensor as shown in FIG. 8. The ion mill resistant layer 708 protects both the hard bias 704 and CMP stop layer 706 during the ion milling. After ion milling, the ion mill resistant material 708 is removed by CMP. The CMP stop layer 706 protects the hard bias layer 704 during CMP.

A NMP solution 901 may then be applied as shown in FIG. 9 to assist removal of the 408. This leaves a structure as shown in FIG. 10. Then, a chemical mechanical polishing process can be performed, leaving a structure as shown in FIG. 11. In addition to removing the ion milling resistant layer 708, the CMP also removes the fences 1002 (as shown in FIG. 10) that may form when portions of the alumina layer 702 extend upward after ion milling. Because the chemical mechanical polishing (CMP) can remove the alumina layer 702, there is a choice as to whether the previous ion milling can be used to remove the alumina 702 above the plane of the sensor 404. The ion milling can either be terminated when the alumina has been reached (as in FIG. 8) or can be continued until this portion of the alumina layer 702 has been removed. A reactive ion etching (RIE) can then be performed to remove the remaining CMP stop material 406, 706. The RIE is performed in a chemistry that is chosen to preferentially remove the material that was chosen as the CMP stop layers 406, 706. This leaves a structure as shown in FIG. 11, with the sensor layers 404 exposed and no fences. Then, with reference to FIG. 12, an electrically conductive, magnetic material such as NiFe 1202 is deposited to form a second electrically conductive, magnetic shield/lead 1202.

The above description illustrates a method for manufacturing a narrow read-width magnetoresistive sensor using a single layer mask of non-silicon containing resist. A mask with an optional Bottom Anti-Reflective Coating (BARC) formed over a CMP stop layer can also be constructed as will be described herein below.

With reference now to FIGS. 13 through 20, a method is described for using a bi-layer mask structure to construct a magnetoresistive sensor having a further reduced read-width. With particular reference to FIG. 13, a first or lower magnetic, electrically conductive shield/lead 402 is formed, and a plurality of sensor layers 404 are deposited over the shield/lead 402 as described earlier. Also as described earlier, a CMP stop layer 406 is deposited over the sensor layers 404, and as before, the CMP stop layer 406 can be constructed of a material such as Ru, Rh, It or Diamond Like Carbon (DLC). A bi-layer mask 1302 is deposited over the CMP stop layer 406. The bi-layer mask includes a first layer 1304 which serves as a release layer, an ion milling mask layer, and which may also be a material that can function as a bottom-antireflective coating (BARC) layer. The layer 1304 may also function as an image transfer layer as will be seen. The layer 1304 can be a soluble polyimide material such as DURAMIDE® or a soluble spin-on carbon material such as SIUL® from SHIN ETSU. A layer of non-silicon-containing photoresist 1306 is then deposited over the first layer 1304.

Then, the photoresist layer is photolithographically patterned to form a read width defining mask as shown in FIG. 14. Because the layer 1304 acts as an image transfer layer to withstand the future ion milling that will be used to construct the sensor, the photoresist layer 1306 can be made thinner than with the previously discussed method. This reduced photoresist thickness means that the photoresist layer can be patterned with greater resolution than with the previously described method, allowing further reduction of read-width. The presence of a bottom antireflective coating (BARC) further improves photolithographic resolution, allowing even further reduced read width. As with the previously described method, the use of a non-silicon containing photoresist provides improved resolution at narrow read width and improved temperature resistance.

With reference now to FIG. 15, a reactive ion etching (RIE) is performed to remove portions of the layer 1304 that are not protected by the photoresist mask 1306 in order to transfer the image of the photoresist layer 1306 onto the underlying layer 1304. The RIE may also be used to further transfer the image of the photoresist mask onto the underlying CMP stop layer 406. Moreover, the RIE can be used to further reduce the read width (RIE slimming) using, as mention previously, O₂, CO₂ or CO₂ with noble gases as mention above. The addition of the noble gas to the CO, can be used to slow the rate of the reactive ion etching. This is useful when patterning with a non-Si-containing resist, which has less resistance to reactive ion milling. In prior art processes that used Si-containing resist, the Si formed an oxide which provided robustness against reactive ion etching. Since the present invention uses a non-Si-containing resist, 1302, the slowing of the etching by the addition of a noble gas helps to ensure that the resist mask 1306 will be sufficiently able to withstand the RIE to allow the mask and sensor to be patterned. Moreover, because the photoresist 1306 is a non-Si-containing photoresist, the etch selectivity is similar to 1304 and 406 which enables uniformity slimming of the stencil (1306, 1304, and 406).

With reference now to FIG. 16, an ion milling is performed to define the sensor width, and then a thin layer of insulation 1602 such as alumina and a layer of hard magnetic bias material 1604 are deposited. As with previously discussed embodiment, the insulation layer 1602 can be deposited by chemical vapor deposition or atomic layer deposition. The hard magnetic bias layer is preferably deposited thicker than the insulation layer and preferably to a thickness that is at least level with the top of the sensor layers 404. As discussed above, a chemical mechanical polishing process can be used to remove the remaining mask 1304. This would require either inserting a CMP stop layer such as Ta with Rh, Ru or Ir, or separately depositing a CMP stop layer such as DLC.

However, as discussed previously, an optional ion milling assisted lift-off in conjunction with CMP can be used to remove the remaining mask 1304 at very small sensor widths. Again, if such an ion milling assisted lift off process is performed, a second layer of CMP resistant material 1606 is deposited, followed by a layer of ion milling resistant material 1608. The materials for layers 1606, 1608 can be the same materials described above with reference to layers 706, 708 of FIG. 7. With reference now to FIG. 17, an ion milling is performed at a glancing angle to remove hard bias material 1604 from the sides of the remaining mask structure 1304. Again, this ion milling can be performed at an angle of 0 to 30 degrees relative horizontal (i.e. relative to the plane of the as deposited layers as much as possible without damage to the substrate fixture). A wrinkle bake step can be performed, and a hot NMP solution 1802 can be applied as shown in FIG. 18. The hot NMP removes the remaining mask 1304, leaving a structure such as shown in FIG. 19. A buff CMP can then be performed to remove the remaining CMP resistant layers 708, 1606, leaving a structure as shown in FIG. 20. A reactive ion etching (RIE) can be performed to remove the remaining CMP stop layers 406, 1606 if DLC is used as the CMP stop layers. A magnetic layer can then be deposited to form a second magnetic shield/lead layer 1202 as described above with reference to FIG. 12.

FIGS. 21-28 illustrate yet another method for manufacturing a magnetoresistive sensor. According to this method a tri-layer mask structure is used to even further reduce read width. With reference to FIG. 21, a first magnetic, electrically conductive shield/lead layer 402 is formed, a series of sensor layers 404 are deposited over the shield/lead layer 402, and a CMP stop layer 406 is deposited over the sensor layers 404. The CMP stop layer can be Ru, Rh, Ir or DLC as before.

A tri-layer mask 2102 is deposited over the sensor layers 404 and CMP stop layer 406. The tri-layer mask includes a release layer 2104 formed at the bottom of the mask structure 2102. The release layer can be a soluble polyimide material such as DURIMIDE® and in addition to functioning as a release layer for assisting in lifting off the mask 2102 also functions as an image transfer layer. A bottom antireflective coating (BARC) 2106 is deposited over the release layer 2104. The BARC layer 2106 can be a Si containing BARC or can be a carbon-only BARC. A non-silicon containing photoresist layer 2108 is deposited over the BARC 2106. A major function of the BARC is to improve resolution of the imaging of the photoresist layer 2106 and may also improve RIE selectivity between the BARC layer 2106 and the release layer 2104. RIE selectivity allows for adjustment of the height of the release/image-transfer layer 2104 to serve as an effective hard mask to pattern the sensor layers 404 and assist in lift-off. A BARC 2106 consisting of carbon only is used to improve photoresist resolution and also reduce faceting during RIE, while silicon containing BARC offers better imaging resolution and also RIE selectivity between the BARC 2106 and the underlying lift off layer 2104.

With reference to FIG. 22, the non-Si-containing photoresist layer 2108 is photolithographically patterned. Then, a reactive ion etching is performed to transfer the image of the photoresist layer 2108 onto the underlying mask layers 2106, 2104 and possibly the CMP stop layer 406 as well, leaving a structure as shown in FIG. 23. CO1 or CO₂ with noble gaseous RIE chemistries as mention previously is used for layers 2104 and 406 while CF₄, CHF₃ or their mixture is used for layer 2104. Then, an ion milling is performed using the mask 2102 as a stencil to form the sensor 404 that are not protected by the mask 2108, 2106, 2104, thereby defining a sensor width and leaving a structure as shown in FIG. 24. The height of the overall mask 2102 is chosen to achieve the narrowest dimension while also being sufficiently thick for patterning of the sensor by ion milling and liftoff.

A thin insulation layer such as alumina 2502 is then deposited, preferably by chemical vapor deposition or atomic layer deposition, and a hard magnetic material 2504 is deposited over the insulation layer 2502, leaving a structure as shown in FIG. 25, with a bump 2506 formed over the sensor structure 404. A thin CMP resistant material 2506, and thin ion milling resistant material 2508 are also deposited as shown in FIG. 25. A chemical mechanical polishing can be used to remove the bump 2506 and to remove the remaining mask 2104. As discussed above, this CMP alone can remove the bump and mask for relatively large sensor widths. However, at very small sensor widths (less than 40 nm) the correspondingly small bump 2504 cannot be removed by CMP alone, and an ion milling assisted CMP lift-off process such as that described above can be used.

An ion milling is performed at a glazing angle as indicated by arrows 2602. This glazing angle is nearly perpendicular to normal or nearly parallel with the planes of the deposited layers. For example, the glazing ion milling can be performed at an angle of 0-30 degrees relative to the planes of the as deposited layers as much as possible without damage to the substrate fixture. This removes the magnetic material 2504 from the sides of the sensor 2104 as shown in FIG. 26. Then, a hot NMP solution can be applied to lift off the mask 2104, and a chemical mechanical polishing can be performed as described above, leaving a structure a shown in FIG. 27. A reactive ion etching can be performed to remove the CMP resistant layers 406, 2506, leaving a structure as shown in FIG. 28.

While various embodiments have been described above, it should be understood that they have been presented by way of example only and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. 

1. A method for manufacturing a magnetoresistive read sensor, comprising: depositing a plurality of sensor layers; depositing a non-Si-containing photoresist over the plurality of sensor layers; patterning the non-Si-containing photoresist to define a sensor width; and performing an ion milling to remove a portion of the plurality of sensor layers that are not protected by the photoresist, thereby forming a magnetoresistive sensor.
 2. The method as in claim 1 further comprising, after depositing the plurality of sensor layers and before depositing the non-Si-containing photoresist, depositing a layer of material that is resistant to chemical mechanical polishing.
 3. The method as in claim 2 wherein the material that is resistant to chemical mechanical polishing comprises Ru, Rh, Ir or diamond like carbon.
 4. The method as in claim 1 further comprising, after performing the ion milling: depositing a non-magnetic, electrically insulating layer; depositing a hard magnetic layer; and performing an ion milling at a glancing angle; and lifting off the photoresist mask.
 5. The method as in claim 3 wherein the glancing ion milling is performed at an angle of 0-30 degrees relative to the planes of the as deposited sensor layers.
 6. The method as in claim 2 further comprising, after performing the ion milling: depositing a layer of non-magnetic, electrically insulating material; depositing a magnetic material over the non-magnetic, electrically insulating material; depositing a second layer of material that is resistant to chemical mechanical polishing; depositing a material that is resistant to ion milling; performing a glancing ion milling; and performing a chemical mechanical polishing.
 7. A method for manufacturing a magnetoresistive read sensor, comprising: depositing a plurality of sensor layers; depositing a release layer; depositing a non-Si-containing photoresist over the plurality of sensor layers; patterning the non-Si-containing photoresist to define a sensor width; performing a reactive ion etching to transfer the image of the photoresist onto the release layer; and performing an ion milling to remove a portion of the plurality of sensor layers that are not protected by the photoresist, thereby forming a magnetoresistive sensor.
 8. The method as in claim 7 wherein the ion milling is performed in an atomstphere that includes CO₂ and an inert gas that is chosen to slow the reactive ion etching process.
 9. The method as in claim 7 wherein the release layer is a material that can also function as a Bottom Anti-Reflective Coating (BARC).
 10. The method as in claim 7 wherein the release layer is a soluble polyimide.
 11. The method as in claim 7, further comprising: after depositing the sensor layers and before depositing the release layer, depositing first layer of material that is resistant to chemical mechanical polishing; and after performing the ion milling: depositing a layer of non-magnetic, electrically insulating material; depositing a magnetic material over the layer of non-magnetic, electrically insulating material; depositing a second lager of material that is resistant to chemical mechanical polishing; depositing a layer of material that is resistant to ion milling over the second layer of material that is resistant to chemical mechanical polishing; performing a glancing ion milling; and performing a chemical mechanical polishing.
 12. The method as in claim 11 wherein the first and second materials that are resistant to chemical mechanical polishing each comprise Ru, Rh, Ir, or diamond like carbon, and the material that is resistant to ion milling comprises Ta or Al₂O₃ Si₃N₄, SiO₂, Ta₂O₅ or DLC.
 13. The method as in claim 6 wherein the first and second materials that are resistant to chemical mechanical polishing each comprise Ru, Rh, Ir, or diamond like carbon, and the material that is resistant to ion milling comprises Ta or Al₂O₃ Si₃N₄, SiO₂, Ta₂O₅ or DLC.
 14. The method as in claim 11 wherein the glancing ion milling is performed at an angle of 0-30 degrees relative to the plane of the as deposited sensor layers.
 15. A method for manufacturing a magnetoresistive read sensor, comprising: depositing a plurality of sensor layers; depositing a release layer; depositing a Bottom Anti-Reflective Coating (BARC); depositing a non-Si-containing photoresist over the plurality of sensor layers; patterning the non-Si-containing photoresist to define a sensor width; performing a reactive ion etching to transfer the image of the photoresist onto the release layer; and performing an ion milling to remove a portion of the plurality of sensor layers that are not protected by the photoresist, thereby forming a magnetoresistive sensor.
 16. The method as in claim 15 wherein the BARC is a carbon-containing BARC.
 17. The method as in claim 15 wherein the BARC is a Si-containing BARC.
 18. The method as in claim 15 wherein the reactive ion etching is performed in an atmosphere containing CO₂ and a noble gas, the noble gas being added in a concentration to slow the reactive ion etching to protect the non-Si-containing photoresist.
 19. The method as in claim 15, further comprising: after depositing the sensor layers and before depositing the release layer, depositing first layer of material that is resistant to chemical mechanical polishing; and after performing the ion milling: depositing a layer of non-magnetic, electrically insulating material; depositing a magnetic material over the layer of non-magnetic, electrically insulating material; depositing a second layer of material that is resistant to chemical mechanical polishing; depositing a layer of material that is resistant to ion milling over the second layer of material that is resistant to chemical mechanical polishing; performing a glancing ion milling; and performing a chemical mechanical polishing.
 20. The method as in claim 19 wherein the first and second layers of material that are resistant to chemical mechanical polishing each comprise Ru, Rh, Ir or diamond like carbon, and the layer of material that is resistant to ion milling Ta or Al₂O₃, Si₃N₄, SiO₂, Ta₂O₅ or DLC. 